Small hotel in the air (6)
I believe the answer is:
skinny
'small' is the definition.
'hotel in the air' is the wordplay.
'hotel' becomes 'inn' (inn is a kind of hotel).
'in' is an insertion indicator.
'the air' becomes 'sky'.
'inn' inserted inside 'sky' is 'SKINNY'.
(Other definitions for skinny that I've seen before include "Thin, bony" , "Emaciated" , "Lacking food" , "Underfed" , "Not very well-built" .)